Electronic devices within the scope of the present invention and in particular smartcards for RFID applications usually consist of an IC, packaged in a module, which is then connected with an antenna and subsequently integrated into a cardbody. For standard cards, normally the module is attached to a substrate foil, in which the insulated wire antenna is embedded and attached by a welding process to the module. This substrate foil then is called an inlay, which, in a separate step, is laminated into the final RFID card.
An alternative way to produce an inlay uses a so-called direct chip attach process. In that case, the antenna consists of a structured layer of a conductive material, such as a thin metal foil, conductive ink, a galvanic plated layer etc., and the IC is connected directly to the antenna via, e.g., a flip chip process.
For example in WO 2007/075352 A2 there is disclosed a method for the assembly of electrical devices and in particular for the assembly of RFID interposes and/or devices. This known method includes heat embedding a chip having bond pads (e.g. bumps) in a substrate and coupling the chip to an antenna element on an upper surface of said substrate. In such a process, the step of providing the antenna structure on a surface of the substrate layer and the step of contacting the antenna structure with the chip are separate, thereby giving rise to procedural inconvenience.
In order to couple the chip with the antenna structure the assembly is compressed. During compression the bumps of the chip penetrate the substrate to establish contact with the antenna structure on the upper surface of the substrate. During compression, considerable stress is applied to the chip in the region of the bond pads or bumps so that delicate structures of the chip should not be arranged in the region neighbouring the bumps and the chip in general should have a thickness sufficient to offer the necessary strength.
In all the described approaches, the actual transponder inlay is not flat, so that additional layers have to be added to compensate for the thickness differences to give a prelam, which then again can be laminated or glued into the final card. Structures using modules currently result in a minimum thickness of around 300 μm. Structures using direct chip attach reveal the disadvantage that the IC is more or less unprotected during the lamination process, which limits the IC thickness to around 100 μm in order to give reasonable die strength values. Assuming a flip chip process, additional bumps are required, which also can be seen as critical for mechanical reliability of the final product, since the stress concentration underneath the bumps is high.
Hence, it is an object of the invention to provide a method for manufacturing electronic devices, in which the above-mentioned disadvantages of the methods according to the state of the art are overcome.